Integrated circuits exist today that include a GaN power FET together with a gate driver and are available in a single monolithic package. This allows for a standard PWM signal (from a micro-controller or PWM controller IC) to be used as a simple input for turning the power FET on and off. These products, such as that illustrated in FIG. 1, include a VCC supply pin, a PWM gate drive input, a VDD supply pin, a DZ Zener reference pin, the power FET drain connection, and the power FET source connection. The connection between the gate drive output and the gate connection of the power FET is internal. This configuration is a tremendous breakthrough invention for the field of power electronics and helps to solve the fundamental problems of noise and transient immunity for a GaN power FET operating under high-frequency and high slew rate (dv/dt) switching modes, and provides additional flexibility for programming the desired turn-on slew rate of the device.
To further improve upon this design, it is desirable to use this device in a floating high-side configuration while still driving the device from a standard low-side referenced PWM signal. Existing solutions, such as that illustrated in FIG. 2 require an additional high-side driver IC or half-bridge driver IC to voltage shift the PWM signal from the low-side, across the isolation or high-voltage barrier, to the high-side. Such solutions, however, have frequency limitations, have propagation delay limitations, consume high currents, require additional PCB footprint area, and are costly. A new solution is needed that is simple and reliable, runs at high-speeds and low propagation delays, and easy to integrate into an existing GaN power FET and gate driver monolithic circuit.